Network identity APIs can cut fraud and create new liability

A customer attempts a high-value transfer from a new device. The bank calls a network API to check whether the phone number matches the current mobile session and whether a recent SIM change appears. The signals can interrupt account takeover. They can also be stale, unavailable or misunderstood.

GSMA's 2026 report identifies fraud prevention and identity verification among use cases for standardised network APIs. The security value sits in a chain of controls. Liability appears where one company treats another company's signal as a guarantee.

Threat: stolen credentials

An attacker has the customer's password and tries to log in. Number verification can show that the current mobile session corresponds to the declared number without relying on an SMS code.

The response needs semantics. Does a match refer to the SIM, subscriber account or device session? How fresh is it? A bank that interprets the wrong entity can approve the wrong risk.

Document that interpretation in the control inventory and train fraud, support and audit teams on the same definition. A model feature named match can drift into several meanings across policy papers, code and customer explanations unless one owner controls it.

Wi-Fi, roaming, dual SIM and corporate subscriptions can produce indeterminate or unsupported results. The application should distinguish those states from a negative match.

If the API is unavailable, fallback cannot quietly remove the second factor. The bank needs a risk-based alternative and a record.

Threat: SIM swap

An attacker persuades or corrupts a process to replace the customer's SIM. A recent-change signal can trigger delay or stronger review.

The look-back window matters. A swap performed just outside a fixed period may pass. A legitimate customer replacing a lost SIM can be locked out during an urgent payment. The bank chooses the action, not the signal provider.

Carrier records need timely updates. Number porting and system delay can create false results. Operators should report known latency and correction processes.

Who pays if a carrier reports no recent change when its own record was late? Contracts often limit the API to information with exclusions. The bank remains accountable for the decision it designs.

Threat: social engineering

The customer controls the genuine SIM and authorises a transfer after deception. Network identity can pass every test. Confirmation of beneficiary, behavioural controls and warnings address another part of the fraud.

Marketing an identity API as a fraud solution can lead buyers to over-rely on it. Threat models should show attacks the signal detects, partly informs and cannot address.

Measure incremental loss reduction against a control group or phased baseline where ethical and feasible. A fall in fraud after launch can coincide with other changes.

Customer education should not transfer all liability. Review interface, alerts and support alongside the customer's action.

Threat: API credential theft

An attacker steals the merchant's API key and queries subscriber signals or runs up charges. Scope, rate limits, network restrictions, rotation and anomaly monitoring protect the interface.

Return minimal information. A boolean or bounded status may serve the control without exposing subscriber details. Logs should support investigation and follow retention limits.

Consent and legal basis need to cover the request. A carrier's technical ability to answer doesn't permit every business to query every number.

The platform must revoke credentials quickly and tell operators and customers which requests were affected. Audit trails need synchronized time and a common identifier.

Threat: false positive and exclusion

A legitimate customer is blocked because the signal is wrong or unsupported. The immediate harm can be missed rent, supplier payment or emergency access.

Provide another verification route and an appeal. Support should see enough reason to help without revealing security rules to an attacker. Track false-positive restrictions and affected groups where lawful.

Operator and API customer need a correction channel. Updating the bank's case without correcting the network record repeats the problem.

A service-level credit paid to the bank does not compensate the end customer. Consumer terms and law determine remedy.

Build the liability map

Place the customer, bank, API platform and operator on one page. For each, record data supplied, control performed, promise made and limit of responsibility.

The operator can warrant service process and still avoid guaranteeing fraud outcomes. The platform can warrant routing and depend on carrier data. The bank combines evidence and decides. The customer receives terms from one or more parties.

Incident cooperation needs deadlines and evidence rights. Broad indemnities can be unenforceable or commercially unavailable. The residual loss should reach the board before launch.

Insurance policies may treat cyber, crime and professional liability differently. Check coverage for API-dependent decisions.

Operate the control as evidence changes

Review match, failure, indeterminate, latency, blocked transactions, appeals and confirmed fraud. Segment by operator and market. Protect customer privacy.

Version changes can alter response fields. Test before production and preserve the model or rule using each version. A historical decision should be reproducible.

Run outage exercises. Decide whether to lower limits, require another factor or pause selected transactions. Communicate without advertising a bypass.

Network identity can remove the weakness of some message-based verification and give banks fresh signals. It works as one control. Describing it that way improves both security and accountability.

Sources

• GSMA, 16 June 2026: The Mobile Economy Africa 2026